The present invention relates to a cooling arrangement for a vehicle for controlling the temperature of and the cooling of a gaseous medium conducted in a pathway leading to an operation of the engine.
The amount of air which can be supplied to a supercharged combustion engine depends on the pressure of the air but also on the temperature of the air. Supplying a largest possible amount of air to the combustion engine entails cooling the compressed air in a charge air cooler before it is led to the combustion engine. The compressed air is usually cooled, in a charge air cooler situated at a front portion of a vehicle, by surrounding air. The compressed air can thus be cooled to a temperature substantially corresponding to the temperature of the surroundings. In cold weather conditions the compressed air in the charge air cooler is cooled to a temperature which may be below the dewpoint temperature of the air, resulting in the precipitation of water vapour in liquid form in the charge air cooler. When the temperature of the surrounding air is below 0° C., there is also risk of the precipitated water freezing to ice within the charge air cooler. Such ice formation will cause a greater or lesser degree of obstruction of the air flow ducts within the charge air cooler, resulting in a reduced flow of air to the combustion engine and hence operational malfunctions or stoppages.
The technique known as EGR (Exhaust Gas Recirculation) is a known way of recirculating part of the exhaust gases from a combustion process in a combustion engine. The recirculating exhaust gases are mixed with the inlet air to the combustion engine before the mixture is led to the cylinders of the combustion engine. Adding exhaust gases to the air causes a lower combustion temperature resulting inter alia in a reduced content of nitrogen oxides NOx in the exhaust gases. This technique is used for both Otto engines and diesel engines. The recirculating exhaust gases are cooled in at least one EGR cooler before they are mixed with the inlet air. The use of EGR coolers in which recirculating exhaust gases are cooled by surrounding air is a known practice. The recirculating exhaust gases can thereby likewise be cooled to a temperature substantially corresponding to the temperature of the surroundings. Exhaust gases contain water vapour which condenses within the EGR cooler when they are cooled to a temperature below the dewpoint of the water vapour. In cases where the temperature of the surrounding air is below 0° C., there is also risk of the condensed water freezing to ice within the EGR cooler. Such ice formation will cause a greater or lesser degree of obstruction of the exhaust flow ducts within the EGR cooler, thereby increasing the content of nitrogen oxides in the exhaust gases.